Paper, plastic, glass and metal substrates and shaped objects have been decorated by transfer printing with a sublimation ink. According to this process, a sublimation ink is first applied to an ink carrier media such as a paper sheet. The ink carrier is held in contact against the surface of the object to be decorated by mechanical means such as a stretchable sheet. The ink carrier media and the surface of the object being decorated are heated to an elevated temperature such that the ink sublimes to a vapor phase that prints onto the surface being decorated. Sublimation inks are made with dispersed dyes such as azo dyes, nitroarylamine dyes or anthraquinone dyes, that when heated, sublime to a gaseous state without passing through a liquid or melt state. These gaseous ink vapors print the surface of the object being decorated.
A device for use in the sublimation printing of shaped objects is disclosed in U.S. Pat. No. 5,893,964 and includes a flexible membrane. An object to be decorated is surrounded with a printed sublimation ink carrier media and placed inside the flexible membrane which is then sealed and evacuated. The atmospheric air pressure outside the flexible membrane presses the ink carrier media against the object to be decorated. The object, ink carrier media, and flexible membrane are then heated to the sublimation temperature of the ink such that the ink sublimes to an ink vapor which prints the surface of the object being decorated.
Sublimation printing of a three dimensional shaped object using a paper ink carrier media has the disadvantage that the paper cannot properly conform to the shape of the surface being decorated. When a flat paper ink carrier is pressed against a three dimensional object, the paper crumples or creases, which causes discontinuities in the image printed on the object surface.
Attempts have been made to overcome this problem by using an ink carrier media that conforms to the surface of a three-dimensional surface being printed. U.S. Pat. No. 5,308,426 discloses ink support materials made of woven fabric, knitted fabric or non-woven material. Although sublimation ink support fabrics offer greater ability to conform to shaped objects than paper, they still exhibit a variety of drawbacks. Many fabrics, such as conventional woven and non-woven fabrics, are not sufficiently flexible and stretchable to be able to conform to the surface of a three dimensional shaped object. Such fabrics bunch or crumple when pressed against a shaped object being decorated in much the same way as occurs with a paper ink support media.
Knit fabrics have been used as a sublimation ink support carrier because they are more extensible than other fabrics and can therefore better conform to the shape of an object. While this extensibility is beneficial during the sublimation step, the same property makes it more difficult to print the sublimation ink onto the carrier media. In many printing processes, such as silk screen printing, heliographic printing and ink jet printing, each color of a design is printed separately, and if the carrier media being printed stretches or contracts between the printing of the various colors, the result is a blurred printed image on both the ink carrier media and the decorated object. In addition, with extensible knitted fabric sublimation ink carriers, when the fabric is stretched over a shaped object during sublimation printing, void spaces in the fabric open up which reduces the sharpness and clarity of the image that is sublimation printed. Along the same lines, extensible knitted fabrics have the property that they are quite porous, especially when stretched. This porosity allows the sublimed ink vapors to pass from the ink carrier media in both the direction of the object being decorated and in the direction of the surrounding flexible membrane such that the flexible membrane quickly becomes contaminated with sublimation inks unless an additional disposable protective sheet is inserted between the ink carrier media and the flexible membrane. Otherwise, during subsequent decorations, the sublimation inks deposited on the membrane can pass back through the porous ink carrier media and randomly deposit on the surface being decorated.
European Patent No. EP 950 540 and U.S. Pat. No. 5,962,368 disclose sublimation ink carrier media comprised of shrinkable films that can be heated so as to conform to the shape of the object being printed. Shrinkable films have the disadvantage that they are difficult to conform to complex shapes. A further disadvantage of shrinkable films is that they often continue to shrink during the sublimation transfer step which tends to cause blurring of the decorated image. Finally, shrinkable films tend to be time consuming to remove after the sublimation step is complete.
As described above, there is a need for a sublimation ink carrier media that does not deform when it is being printed with a pattern or design, but that does extend during sublimation so as to conform to the shape of an object being decorated. There is a further need for a sublimation decoration process with a sublimation ink carrier media that can extend around and conform to the surface of a three dimensional object being decorated, but that does not open up when stretched such that the sublimated decoration loses clarity. Finally, there is a need for a flexible and extensible sublimation ink carrier media and sublimation decoration process wherein the ink carrier media can serve as the sole flexible membrane during the ink sublimation process with no further need for additional protective sheeting outside the ink carrier media.